The present invention broadly relates to an actuating or drive device and, more specifically, pertains to a new and improved construction of an actuating or drive device for a high-voltage switch.
Generally speaking, the actuating or drive device of the present invention, which is used for high tension or voltage switches, is of the type comprising at least one actuating or cut-off spring which is cocked or tensioned in the switch cut-on or closed position. This actuating or cut-off spring is operatively coupled with a switching or actuating linkage or rod leading to a set of movable contacts of the switch. Means are provided in order to variably or non-uniformly modify, during a cut-off or opening stroke and as a function of the stroke, the force generated by the actuating or cut-off spring and effective upon the actuating linkage or rod.
In the case of high-tension or voltage switches the switch opening or cut-off stroke of the actuating device is one of the most important and critical motions. At the beginning of the switch opening or cut-off stroke the movable components, i.e. the movable switch contact points or set of movable contacts, must be rapidly accelerated from the stationary state. Then the switch cut-off stroke must be rapidly executed in order to obtain a rapid extinction of the switching arc. Finally, at the end of the switch opening or cut-off stroke, any small forces that may be still acting in the direction of the opening or cut-off stroke must be accommodated.
In order to accomplish this the German Pat. No. 1,806,951, granted Jan. 27, 1977, discloses using a series or tandem arrangement of two springs as the actuating or cut-off spring, the first of which has a steeper spring characteristic and a smaller displacement, perhaps limited by a stop, while the second spring has a flatter spring characteristic and a longer spring displacement. This results in a force-displacement diagram for the switch opening or cut-off stroke which at first falls steeply as long as the first spring is effective and then, following a discontinuity, runs considerably flatter, since only the second spring is effective. This force-displacement relationship may be suitable for the switch opening or cut-off stroke, but it is the reverse or mirror image for the switch closing or cut-on stroke. While at the beginning of the switch closing or cut-on stroke at first only the second, weaker spring must be compressed, suddenly the first, stiffer spring must also be compressed. That is, in the execution of a switch closing or cut-on stroke the switch cut-on drive is subjected to a shock which can lead to undesirable vibrations in the actuating or drive system.
In Swiss Pat. No. 391,058, granted Apr. 30, 1965, an actuating or drive device is described in which a single actuating or cut-off spring directly drives the actuating linkage or rod by means of a crank. A two-stage hydraulic device is arranged in parallel with the actuating or cut-off spring. It is employed as a damping device during the switch opening or cut-off stroke and as a hydraulic drive during the switch closing or cut-on stroke. In this case, the motion induced by the force of the actuating or cut-off spring at the beginning of the switch opening or cut-off stroke is damped relatively little and later more. At the beginning of the switch closing or cut-on stroke this prior art arrangement must first supply a maximum force which then diminishes towards the end of the switch closing or cut-on stroke. The maximum force is obtained by furnishing pressurized fluid from a pressure storage means or from a pump. In addition to this disadvantage, this construction entails considerable technical complications.